1. Field of the Invention
The present invention relates to a method of fabricating a solar cell, and more particularly, to a method of fabricating an electrode structure of a solar cell.
2. Description of the Prior Art
Because of the limited amount of non renewable energy sources, the demand for substitute energy sources increases with time, and among all kinds of substitute energy sources, the biggest potential is in solar energy. The common function of the solar cell (the photovoltaic cell) is to transfer the radiation energy of the sunlight through the semiconductor materials to produce electrical energy. The solar cell may include semiconductor materials such as silicon substrate made of single crystalline silicon, poly crystalline silicon, or amorphous silicon, and electrodes made of conductive paste such as silver (Ag) paste.
Screen printing technology is usually utilized to form the electrodes of solar cells in order to reduce manufacturing costs and time. Manufacturers form a frame having the predetermined patterns at first, and the predetermined patterns could be further printed on the substrate according to the frame. For example, an anti-reflective layer made of silicon nitride is firstly formed on the substrate, and then conductive paste is applied to the substrate through the frame. The predetermined patterns are therefore formed on the substrate. Furthermore, the anti-reflective layer is located between the conductive paste and the substrate. Subsequently, a high temperature heating process, such as a heating process with a processing temperature around 700 degrees (° C.) is performed to burn the anti-reflective layer, so that the conductive paste can pass through the burned anti-reflective layer to form an ohmic contact between the conductive paste and the corresponding substrate surface, accordingly, the predetermined electrode structures including bus bar electrodes and finger electrodes are completed. Finger electrodes formed on the radiation-receiving front surface are usually used to receive and conduct photoelectric currents from the substrate to the bus bar electrodes. However, opaque finger electrodes may cover a part of the radiation-receiving front surface, and the light absorbing area of the solar cell inevitably decreases, thereby adversely affecting the power conversion efficiency of the solar cell. In the conventional solar cells having finger electrodes, the covered area rate of the radiation-receiving front surface is between 7% and 8%. Moreover, with the increasing price of silver paste, the manufacturing costs of electrode structures raise. Additionally, the manufacturing costs of the screen printing technology can be absorbed only through mass production.
Consequently, how to improve the manufacturing process of electrode structures of solar cells in order to increase the light absorbing area and decrease the unit cost of a small production or a customized production is still an important issue in the field.